This invention relates to laboratory testing procedures and, more particularly, to a method and apparatus for accurate, reproducible examination of urine specimens and the like.
In the field of clinical testing, the analysis of urine samples is carried out as a common routine to determine, for example, the amounts of sugar, albumin, and solids present in the specimen obtained from a patient. The results of such analysis provides a valuable tool for the diagnostician to aid in the determination of pathological conditions in the body, and in the detection of various diseases.
The procedures carried out in the performance of a urinalysis are well known and do not form a part of the present invention. However, it is important to note that microscopic examination of the urine sample forms an integral part of a urinalysis. Urine sediments are examined for cellular elements such as erythrocytes, leukocytes, epithelial cells, casts and crystals, the presence of which in more than normal amounts is an indication of a variety of system malfunctions.
Needless to say, the preparation of the urine specimen for microscopic examination is a critical element of the examination if the results are to be meaningful. In accordance with standard procedure, 12 ml of urine specimen are centrifuged for 5 minutes at 400g, i.e., at 400 times the gravitational acceleration force. The sediment is thereby suspended in about 1 ml of the urine, normally the lower 1 ml portion of the centrifuge tube. The upper 11 ml of sample is decanted off and usually only one drop of the remaining liquid containing suspended solids is taken for microscopic examination.
A highly important step in preparing the sample for microscopic examination is the decanting step to separate the major liquid portion of the sample from the 1 ml portion containing the suspended solids. Thus, for example, should more or less than 11 ml be decanted after centrifuging, the solids suspended in the remaining portion of the urine will be diluted or concentrated abnormally, and the resulting examination may be inaccurate and not reproducible. Likewise, lack of care in the decanting technique may result in the loss of suspended solids, and in correspondingly inaccurate and unreproducible results.
The present invention overcomes the aforementioned deficiencies in urinalysis technique and provides a method and apparatus for sample preparation to achieve accurate and reproducible microscopic examination.